In current storage networks, and particularly storage networks including geographically remote directors (access nodes) and storage resources, preserving or reducing bandwidth between resources and directors is highly desirable. Data access may be localized, in part to improve access speed to data blocks requested by host devices. Caching data blocks at directors provides localization, however, it is desirable that the cached data be kept coherent with respect to modifications at other directors that may be caching the same data. An example of a system for providing distributed cache coherence is described in U.S. Patent App. Pub. No. 2006/0031450 to Unrau et al., entitled “Systems and Methods for Providing Distributed Cache Coherency,” which is incorporated herein by reference. Other systems and techniques for managing and sharing storage array functions among multiple storage groups in a storage network are described, for example, in U.S. Pat. No. 7,266,706 to Brown et al. entitled “Methods and Systems for Implementing Shared Disk Array Management Functions,” which is incorporated herein by reference.
In a distributed cache coherence model employing a dedicated protection memory area, speedy data protection may be provided under certain communication protocols. However, under certain conditions and scenarios, a design based on a dedicated protection memory area may lead to memory waste and may yield sub-optimal data availability.
Accordingly, it would be desirable to provide an efficient cache coherency system and method in connection with storing and managing data shared over a network.